Chronic exposition to ozone induces cardiac antioxidant response and overexpression of either mitochondrial fision protein DRP1 and hipertrophyc-related proteins

Influence of different concentrations of ozone on the alteration of mitochondrial DNA copy numbers in human peripheral blood

By now, O₃ pollution has become a main environmental problem. O₃ is a prevalent risk factor for many diseases, but the regulatory factors linking O₃ and diseases remain ambiguous. Mitochondrial DNA (mtDNA) is the genetic material in mitochondria, which plays a key role in the production of respiratory ATP. Due to a lack of histone protection, mtDNA is easily damaged by ROS, and O₃ is an important source to stimulate the production of endogenous ROS in vivo. Therefore, we logically speculate that O₃ exposure can alter mtDNA copy number by the induction of ROS. In the present study, we performed a panel study of 65 MSc students at the Chinese research academy of environmental sciences (CRAES) with 3 rounds of follow-up visits from August 2021 to January 2022. We examined the mtDNA copy numbers in the peripheral blood of subjects using quantitative polymerase chain reaction. Linear mixed-effect (LME) model and stratified analysis were used to investigate the association between O₃ exposure and mtDNA copy numbers. We found a dynamic process of the association between the concentration of O₃ exposure and the mtDNA copy number in the peripheral blood. The lower concentration of O₃ exposure did not affect the mtDNA copy number. As the concentration of O₃ exposure increased, the mtDNA copy number also increased. While, when O₃ exposure reached a certain concentration, a decrease in mtDNA copy number was found. This correlation between the concentration of O₃ and the mtDNA copy number could be ascribed to the severity of cellular damage induced by O₃ exposure. Our results provide a new perspective for the discovery of a biomarker of O₃ exposure and health response, as well as for the prevention and treatment of adverse health effects caused by different concentrations of O₃.

NO2 exposure contributes to cardiac hypertrophy in male mice through apoptosis signaling pathways

Nitrogen dioxide (NO₂) is one of the most common indoor and outdoor air pollutants. Inhalation of NO₂ is associated with an increased risk of health problems, especially cardiovascular diseases. However, the underlying pathogenic mechanisms still remain unclear. In this study, we exposed C57BL/6J mice to NO₂ (2.5 ppm, 5 h/d) for 28 days and found that NO₂ inhalation induced cardiac dysfunction in male mice, but not in female mice, including left ventricular dilation and cardiac systolic dysfunction. Pathological staining showed that NO₂ inhalation induced eccentric hypertrophy with enlarged individual cardiomyocytes, dilated left ventricle, and thinning of the left ventricular wall in male mice. The transcriptional analysis suggested that NO₂ exposure could disrupt Ca²⁺ homeostasis, actin cytoskeletal reorganization, myocardial contractility, and vascular dilation in male mice. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that differentially expressed genes (DEGs) were closely associated with the apoptotic signaling pathways. These findings suggested that NO₂ exposure caused cardiac eccentric hypertrophy and cardiac dysfunction through apoptotic signaling pathways, and contributed to cardiotoxicity.